Oral Species and Their Connection to Events of Clinical Relevance in Gastrointestinal and Respiratory Tracts.

is recognized as one of the core anaerobic genera in the oral microbiome. In addition, members of this genus belong to microbial communities of the gastrointestinal and respiratory tracts. Several novel species, most of them of oral origin, have been described, but limited knowledge is still available of their clinical relevance. is among the anaerobic commensals on oral mucosae from early months of life onward, and other early colonizing species in the oral cavity include and . Oral species get constant access to the gastrointestinal tract via saliva swallowing and to lower airways via microaspiration. At these extra-oral sites, they play a role as commensals but also as potentially harmful agents on mucosal surfaces. The aim of this narrative review is to give an updated overview on the involvement of oral species in gastrointestinal and respiratory health and disease.